The present invention relates to a chain with a single direction of curvature, that is, in which each link can pass freely only on one side with respect to the line of the axes of the divisor axles of adjacent links; thus, it can pass around two pinions while being practically without flexure between them under the action of a force tending to apply against them.
Chains with a single direction of curvature are known; they are used primarily as conveyors for merchandise. One known construction for such chains is described in French Pat. No. 1,297,285. A similar construction is described in French Pat. No. 2,207,069 (U.S. Pat. No. 3,884,152). This type of chain is perfectly adapted to certain uses, primarily for handling units. On the other hand, they have the inconvenience of not being suitable for small values of pitch, thus for pinions of small diameter, because each link must be small and the requirements of dimensional precision and of strength lead to a prohibitive cost in view of the large number of links therefore necessary.
Another type of chain with a single direction of curvature is described in French Patent Application No. 7420681. The chain has a single direction of curvature and is constituted by a normal chain mounted with blocks which prevent all possibility of bending in the half plane where they are located. But such a chain does not absorb shearing forces, thus the play and the elastic elongation of the links lead to a flexing in the moving portions of the length of chain supported between two pinions. This flexure could become rapidly prohibitive as soon as a sufficient force is applied on this length of chain.